Quantum untanglement: Is spookiness under threat?

POOR old Einstein. He didn’t much like quantum theory, and who can blame him? It’s just so… well, peculiar. Nothing in the quantum world exists until you measure it. Certainty melts away. And then there’s what Einstein famously called “spooky action at a distance”. He didn’t like any of it. Yet experiments show quantum mechanics to be the most accurate physics theory in history. Not only does quantum theory make all the right predictions, physicists largely agree that modern experiments, combined with quantum theory’s mathematics, leave no room for alternatives. There is no competing theory that banishes the weirdness and embraces a reality that exists independent of our observations of it. The spookiness, it seems, is here to stay.

Or is it? Listen to Joy Christian at the University of Oxford and you may wonder if these grandiose quantum conclusions are really necessary at all. He claims that physicists’ supposed proofs of the impossibility of more “realistic” theories rest on false assumptions and so don’t prove much at all.

“Contrary to the received wisdom,” he says, “quantum theory doesn’t rule out the possibility of a deeper theory, even one that might be fully deterministic.” Christian’s conclusion follows from a relatively simple calculation using alternative mathematics, described in a paper now under review at the journal Physical Review Letters.

It is a controversial finding, and many theorists disagree with his result, but if Christian is right, perhaps the angst felt by Einstein and others will have been for naught. Whatever the answer, Christian is by no means alone in questioning whether quantum theory is the “final theory” it is often …